Air cooled condenser apparatus



United States Patent [72] lnventor Addison Y. Gunter Houston, Texas [21] Appl. No. 754,048 [22] Filed Aug. 20, 1968 [45] Patented Dec.l,l970 [73] Assignee Hudson Products Corporation Houston, Texas a corporation of Texas. by mesne assignment [54] AIR COOLED CONDENSER APPARATUS 8 Claims, 3 Drawing Figs.

[52] US. Cl 165/111,

165/99, 165/113, 165/122, 165/134, 165/146 [51] Int.Cl F28b1/06, F28b 7/00; F28f 13/00 [50] Field ofSearch 165/111, 146,147,110,98,99,134,122,113

[56] References Cited UNITED STATES PATENTS 1,486,012 3/1924 Christy 165/98 Primary Examiner-Albert W. Davis, Jr.

Attorney-Hyer, Eickenroht and Thompson ABSTRACT: An air cooled condenser in which successive rows of finned tubes of equal length extend between an inlet header and an outlet header and are adapted to be arranged in the direction of air flow therepast. The fins on each tube of the row first to be contacted by the air flow extend from the inlet header for a lesser length thereof than the fins on each tube of a successive row. An air flow regulating means is provided on the side of the condenser adjacent the last succeeding row of tubes and generally opposite the unfinned lengths of the tubes at their ends adjacent the outlet header. In one embodiment, the condenser is a vent condenser having its inlet header connected in series with the outlet header of a main condenser to receive uncondensed vapors therefrom.

Patented Dec. 1, 1970 3,543,843

A 19 22 T 25 27 29 33 F/G.3 v Addison K Gunter l N VENTOR.

ATTORNEYS Q AIR COOLED CONDENSER APPARATUS This invention relates generally to air cooled condenser apparatus; and, more particularly, to improvements in air cooled condenser apparatus for use in condensing steam or vapors of other liquids having relatively high freezing points.

In the conventional condenser of this type, successive rows of tubes of equal lengths and identical construction are connected in parallel between inlet and outlet headers and are adapted to be arranged in the direction of air flow. There are usually two or more tubes in each such row, and the tubes are often provided with fins for increasing their heat exchanging capabilities.

One serious problem which is encountered in condensers of this type results from the fact that the temperature of the air drops as it flows past the successive rows of tubes. Thus, there is also a drop in the temperature differential between the air and the fluid within the tubes of successive rows of tubes. Consequently, greater amounts of steam will condense in the tubes of the rows nearest the air flow than in the tubes of successive rows.

As a result, the condensable steam in the tubes of the rows nearest the air fiow may be fully condensed a considerable distance from the outlet header. This not only represents poor utilization of the tube surfaces, but also creates a very hazardous situation in environments in which the ambient temperature is considerably below the freezing point of the condensate. That is, the condensate may freeze up and thereby choke the tubes in the first row, which causes the air flow to successive rows to be at a lower temperature so that the tubes of successive rows may also become frozen up.

The steam condensers shown and described in U.S. Pat, Nos. 3,073,575 and 3,223,152 were intended to overcome this problem by balancing or equalizing condensation in all the rows of tubes, so that theoretically condensation would be complete in the tubes of each row at a level substantially adjacent the outlet header. Thus, it was proposed to either vary the distribution of steam to the tubes of the rows of tubes or vary the heat exchanging capacities of the tubes of different rows.

For example, in accordance with one proposal, the tubes of successive rows were provided with successively smaller openings therethrough, either by way of different sizes of tubes or different sizes of orifices in the tubes. In accordance with another proposal, the heat exchanging capacities of the tubes ofsuccessive rows were adjusted by various means, such as fins of different spacing, fins of different sizes, etc. along the lengths of the tubes. Alternatively, it was proposed to employ two or more ofthese tube constructions.

In any case, the steam condensers of these prior patents had in common the fact that each was designed for a particular ambient temperature. Thus, in the event such temperature should fall below or above that for which the condenser was designed, the balance would be upset, resulting in undercooling in the case ofa lower temperature and uncondensed steam in the case ofa higher temperature.

An object of this invention is to provide air cooled condenser apparatus in which freezing up is much less likely than in condensers of the type above described.

Another object is to provide air cooled condenser apparatus in which there is not only a tendency to balance condensation in the various rows of tubes, as in the prior condensers above described, but also an increase in tube side temperature at the outlet header, so that freezing is normally prevented even in the event of ambient temperatures lower than that for which the apparatus was designedv A further object is to provide such apparatus in which there is more accelerated condensation in the last rows of tubes than in prior apparatus of this type, and, more particularly, in which the extent ofthis acceleration may be controlled.

Yet another object is to provide such apparatus in which the finned tubes in the different rows arc of such construction that they may be made in substantially the same manner.

These and other objects are accomplished, in accordance with the illustrated embodiments of the invention, by an air cooled condenser in which the fins of each tube of the row first to be contacted by the air flow extend therealong for a lesser length than the fins of each tube of a successive row. More particularly, the fins on each tube extend from the inlet header so that the unfinned lengths of the tubes are adjacent the outlet header, whereby each tube of the first row has a greater unfinned or bare length adjacent such outlet header than does each tube of the successive row.

As will be appreciated, these unequal lengths of fins tend to equalize condensation in the different rows, and thereby more efficiently utilize the tube surfaces. Also, the unfinned lengths of the tubes maintain the fluid temperature of the inside walls of the tubes of at least the first row of tubes at a relatively high temperature. That is, the overall heat transfer rate between the air and the fluid within the unfinned lengths of the tubes is so low that the temperature of the fluid will be only slightly less than its temperature as it leaves the finned lengths of the tubes. Consequently, even if there is condensation in the ends of the tubes of the first row near the outlet header, the temperature of the condensate will normally be maintained above its freezing point.

This is to be compared, for example, with the above described condensers wherein fins extend the entire length of the tubes of all rows. In such a case, the overall heat transfer rate is quite high, and many times that of the unfinned lengths of the tubes. As a result, the temperature of condensate in the tubes of the first row adjacent the outlet header may be considerably less than the inlet temperature of the tube side fluid, and very possibly below its freezing point.

Since portions of the tubes of the condenser of this invention are unfinned, there is increased air velocity past them, which accelerates condensation in the tubes of the succeeding rows. This is especially true of the row last to be contacted by the air flow where there is ordinarily the least amount of condensation. Fuller use of this feature of the present invention is made possible by the provision of a means for regulating the air flow on the side of the condenser adjacent the last row to be contacted thereby and generally opposite the unfinned lengths of tubes.

In the illustratedembodiments ofthe invention, the tubes of the successive rows differ only in the lengths of fins therealong, although, in other embodiments, the tubes of some rows may be identical in all respects. Thus, in any case, all the tubes may be of equal size, free of orifices or the like, and have fins of equal size and spacing therealong. Standard fin forming practices permit these lengths of fins to be determined within normal operating procedures.

According to one embodiment of the invention, this condenser may be a vent condenser connected in series with and downstream of a main condenser. This, of course, has the advantage of lowering the pressure drop in the vent condenser by removing condensate from the outlet header of the main condenser, so that only uncondensed steam is introduced into the vent condenser. Also, the unused tube lengths resulting from overdesign are reduced proportionately. Still further, the number of tubes in the vent condenser are usually less than in the main condenser.

In the drawings, wherein like reference characters are designated by like parts:

FIG. I is a perspective view of a condenser constructed in accordance with one embodiment ofthe present invention;

FIG. 2 is a side view of the condenser of FIG. 1, with the direction of air flow indicated by an arrow, and

FIG. 3 is a side view of condenser apparatus constructed in accordance with the last-mentioned embodiment of the invention, with the direction of air flow through the main and vent condensers thereofindicated by an arrow.

The condenser illustrated in FIGS. 1 and 2, and indicated in its entirety by reference character 1ft, comprises an inlet header it at one end, an outlet header at the other end, and tubes extending therebetween and thus connected in parallel to one another. More partic rly, the tubes extend successive rows A, B, C, and D w..rch adapted to be arranged to extend in the direction of air flow. Thus, with the air flow being in a vertically upward direction, as shown in FIG. 2, the tubes are disposed generally horizontally so that the first row A of tubes to be contacted by the air flow is the lowermost, and the last row D to be contacted by the air flow is the uppermost.

Although the condenser illustrated in the drawings has four such rows of tubes, this invention contemplates that there may instead be two or three rows, or more than four rows. F urthermore, although each such row is illustrated in FIG. 1 as having a plurality of tubes, this invention further contemplates that each row may instead comprise only a single tube. Still further, and as well known in this art, air flow may be either due to induced draft or mechanical means of some type, neither of which is illustrated herein.

In any case, this cool air flowing upwardly around and between the tubes 13 condenses the vapors in the tubes, which may be'steam. This steam or other vapor is introduced into the inletheader 11 through a port 14, and the steam condensed in the various tubes is removed from the outlet header 12 through a port 15 at its lower end. Noncondensables or uncondensed steam, if there is any, is removed through a port 16 at the upper end of outlet header 12 to an ejector.

As is common in the art, the tubes 13 are provided with fins 17 thereabout for increasing the heat transfer rate between the air on the outside of the tubes and the steam or other vapor on the inside of the tubes. These fins are of equal size and spacing and may be formed on the tubes in any number of well known ways, such as by extrusion, by wrapping about the tube, etc. If desired, the heat transfer rates of the tubes may be further increased by the provision of discontinuities such as louvers or the like on their surfaces.

As previously described, since the air flowing upwardly past the succeeding rows of tubes is progressively heated, the temperature differential between the air surrounding the first or lower row A of tubes and the fluid within such tubes will be greater than the differential between the air surrounding the tubes of the second row B and the fluid therein. In like manner, of course, the temperature differential between the air surrounding the tubes the second row B and the fluid within such tubes is greater than the differential between the air surrounding the tubes of the third row C and the fluid within such tubes. The same may be said, of course, about the third and fourth rows of tubes, or any additional pairs of successively adjacent rows of tubes. Thus, the differential between the air surrounding the tubes of the first row and the fluid in such tubes is greater than the differential between the air surrounding the tubes of any successive row and the fluid in such tubes, whether such successive row be the second, third or fourth row of tubes to be contacted by the air flow.

Thus, the problem of unequal condensation in the rows of tubes is greatest in the first two rows of tubes to be contacted by air flow, less critical in the case of the second and third rows of tubes, and still less critical in the case of the third and fourth rows of tubes. That is, if there is freezing up in the tubes of conventional condensers, it will always occur in the tubes of the first row, and the possibility of additional freezing up in succeeding rows is progressively less likely.

As previously described, and as shown in FIGS. 1 and 2, the fins 17 of the tubes of the first or lower row A extend from the inlet header 11 along a lesser length thereof than the tubes of a successive row, whether it be row B, C, or D. More partlcu- Iarly, in this particular embodiment of the invention, the fins of the tubes of each row extend along a lesser length thereof.

than the tubes of the fins-of the adjacent succeeding row, whereby there is a progressively increasing length of fins along the tubes of all four successive rows.

Since there is a lesser length of fins on the tubes of the first row than upon the tubes of successive rows, there will be a correspondingly lesser amount of heat transfer surface in such row. Due to the particular arrangement shown in the condenser of FIGS. 1 and 2 this is true of the tubes of each row with respect to the tubes of succeeding rows. The desired differences in the amount of heat transfer surface, and thus the particular relationship of the finned lengths of the tubes of different rows to one another in order to substantially balance condensation therein, will depend upon the desired characteristics of the condenser, such as the ambient temperature expected in the environment in which the condenser is to be used. However, these considerations are well known to those skilled in the art, and need not be considered here.

The important thing is that along with this tendency to balance the amount of condensation in the successive rows of tubes, the condenser of this invention maintains the temperature of the condensate within the tubes adjacent the outlet header [2 at substantially the temperature at which it condensed. This in turn greatly reduces the likelihood of freezing up of condensate in the tubes, particularly those on the first or lower row A. That is, as previously mentioned, the heat transfer rate between the air and fluid to be condensed is many times less in the case of unfinned or bare tubes than it is in the case of finned tubes, so that these unfinned lengths of tubes are kept much warmer than would be the finned lengths thereof. I

For example, it can be shown that with an ambient air temperature of 0 F. and an unfinned tube side inlet temperature of 60 F, the tube side outlet temperature of the unfinned tube length, and thus the temperature of condensate therein, could be as high as 56.6 F. on the other hand, with conventional finned tubes, the tube side outlet temperature, and thus the temperature of condensate in the tubes, could be 29 F. Consequently, in this typical example, steam condensed in the tubes of the first or lower row A could be frozen with the use of conventional finned tubes, while the temperature of such condensate in tubes having unfinned lengths, as shown herein, would be well above freezing point.

Since the ambient air is progressively heated as it passes over successive rows of tubes, progressively lesser lengths of unfinned lengths of tubes would be required. Thus, it may be found that only the first two rows of tubes to be contacted by air flow need have unfinned lengths. In fact, it may be found that only the first row need have unfinned lengths of tubes adjacent the outlet header. I

As previously described, and as will be appreciated from the foregoing, there is less resistance to air flowing past the outlet ends of the tubes, so that it has a greater velocity, which is particularly advantageous in accelerating condensation in the last row D. There is a means 18 adjacent the upper side of the condenser and toward the outlet end thereof and generally opposite the unfinned lengths of tubes of the rows of tubes for regulating this air flow. This means may comprise a screen having adjustable openings, louve'rs, or the like, for allowing a greater or lesser flow of air therethrough As shown in FIG. 2, the air regulating means extends generally between the termination of the fins on the first or lower row A of tubes and the outlet header 12.

The air cooled condenser apparatus shown in FIG. 3 comprises a main condenser and a vent condenser, which are designated in their entireties by reference characters 19 and 20, respectively. The main condenser 19 is of generally conventional construction, comprising an inlet header 20 at one end, an outlet header 21 at the other end, and tubes 22 extending therebetween. More particularly, the tubes have fins 23 extending therealong and are arranged in rows extending in the direction of air flow, which is indicated by the arrow in FIG. 3, whereby air is caused to flowsuccessively over the rows of tubes in an upward direction. In accordance with the conventional practice, the fins extend throughout the entire lengthsofthe tubes 22 of allrows from one header to the other.

As in the case of the header 1]. of condenser 10 of FIGS. 1 and 2, the inlet header 20 has a port 24 at its upper end for introducing steam or other vapor to be condensed into the tubes of the condenser. However, the outlet header 21 has a lower port 25 for removing condensate from the tubes of the main condenser, and an upper port for conveying uncondensed vapor from the main condenser to the vent condenser.

The vent condenser 20 also includes an inlet header 27, an outlet header 28, and tubes 29 extending therebetween for connection in parallel with one another. The inlet header 27 has a port 30 therein connected by a conduit 31 to the port 26 of outlet header 21 of main condenser 19 so as to receive uncondensed vapor therefrom, as above described. Outlet header 28 has upper and lower ports 32 and 33, respectively, for connection to an ejector and to discharge condensate.

The vent condenser will normally be connected to the outlet headers of two or more main condensers for receiving uncondensed vapor from each of them, whereby the number of tubes in the vent condenser will be half or even less than half those in the main condenser. Thus, with the tubes 29 of the vent condenser of short length relative to those of the main condenser, as shown in FlG. 3, the total length of tube surface in the vent condenser will be even a smaller fraction of the total lengths of tube surface in the main condenser. Preferably, the two condensers are so designed relative to one another that, in the expected ambient temperature range, condensation will not be complete within the tubes of any of the rows of the main condenser, so that there is no danger of freezing up in the main condenser. Also, since total tube lengths of all the tubes of the main condenser are used to condense, there is a reduction in surface'requirements.

The vent condenser 20 is similar in construction to the condenser of FIGS. 1 and 2. Thus, for example, the tubes 29 of the first or lower row A to be contacted by air flow have lesser lengths of fins 34 therealong than do the tubes of each of the successive rows B, C, and D of tubes. As shown, the vent condenser 21 may also be provided with a means 35 for regulating air flow through the unfinned lengths of the tubes.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed with reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be un derstood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. An air cooled condenser, comprising a pair of headers, successive rows of tubes of equal length extending between the headers and adapted to be arranged in the direction of air flow therepast, and fins on said tubes, the tins of each tube of the row first to be contacted by said air flow extending for a lesser length thereof than the fins on each tube of a successive row.

2. An air cooled condenser of the character defined in claim 1, wherein said successive row is the row adjacent said row first to be contacted by said air flow.

3. An air cooled condenser of the character defined in claim 1, wherein there are at least three successive rows of tubes, with the fins of each tube of each row extending for a lesser length thereof than the tins of each tube of the adjacent successive row.

4. Air cooled condenser apparatus, comprising a main condenser having apair of headers and successive rows of finned tubes extending between the headers and adapted to be arranged in the direction of air flow therepast, a vent condenser having a pair of headersand successive rows of tubes extending therebetween and adapted to be arranged in the direction of air flow therepast, and means connecting a header of the main condenser with a header of the vent condenser, the tubes of the vent condenser having fins thereon with the fins on each tube of the row first to be contacted by said air flow extending for a greater length thereof than the fins on each tube of a successive row.

5. An air cooled condenser, comprising an inlet header, an

outlet header, successive rows of tubes ofequal length extendmg between the headers and adapted to be arranged in the direction of air flow therepast, and fins on said tubes, the fins on each tube of the row first to be contacted by said air flow extending from the inlet header for a lesser length than the fins on each tube of a successive row.

6. An air cooled condenser of the character defined in claim 5, wherein said successive row is the row adjacent said row first to be contacted by said air flow.

7. An air cooled condenser of the character defined in claim 5, wherein there are at least three successive rows of tubes, with the fins of each tube of each row extending for a lesser length thereof than the fins of each tube of the adjacent successive row.

8. Air cooled condenser apparatus, comprising a main condenser having an inlet header, an'outlet header, and successive rows of finned tubes extending between the headers and adapted to be arranged in the direction of air flow therepast, and a vent condenser having an inlet header connected to the outlet header of the main condenser, an outlet header, and successive rows of tubes extending between the headers and adapted to be arranged in a direction of air flow therepast, the tubes of the vent condenser having fins thereon with the fins on each tube of the row first to be contacted by said airflow extending from the inlet header for a lesser length than the fins of each tube of a successive row. 

